The following relates to the nuclear reactor arts, nuclear power generation arts, nuclear safety arts, and related arts.
A conventional pressurized water reactor (PWR) includes a cylindrical pressure vessel containing a nuclear reactor core comprising a fissile material. The reactor core is located near the bottom of the pressure vessel, which is filled with primary coolant water. During operation, the reactor core heats the primary coolant water and the heated water tends to rise. A cylindrical central riser located above the reactor core and coaxially inside the pressure vessel conveys the rising heated water to near the top of the pressure vessel where the heated water discharges and flows back down through a “downcomer” annulus defined between the central riser and the inside wall of the cylindrical pressure vessel to complete the primary coolant flow circuit. This primary coolant circulation can occur naturally (i.e., natural circulation) driven by the heat generated by the reactor core. Additionally or alternatively, a set of reactor coolant pumps can be provided to assist or drive the primary coolant circulation.
In a conventional PWR the primary coolant is piped out of the pressure vessel and into an external steam generator. This steam generator is a heat exchanger in which the piped primary coolant serves as the heat source for heating secondary coolant water flowing through a secondary coolant flow path within the steam generator. Typically, two or more external steam generators are operated in parallel, so as to provide a level of redundancy.
An integral PWR is a design variant in which the steam generator is located inside the pressure vessel. Typically, the steam generator is annular (or a set of steam generators form an annular assembly) that is disposed in the downcomer annulus. The primary coolant flowing downward through the downcomer annulus serves as the heat source, and secondary coolant is flowed into the pressure vessel and upward through the steam generator to remove the thermal energy. The steam generator typically has a tube-and-shell configuration in which an assembly of tubes is surrounded by a shell. In some such configurations, the primary coolant flows downward through the tubes (i.e., tube-side) and the secondary coolant flows upward through the shell (i.e., shell-side). Alternatively, the downward primary coolant flow may be shell-side while the upward secondary coolant flow may be tube-side. The tubes may have various geometries, such as straight vertical tubes, or helical tubes winding around the central riser, or so forth. Integral PWR designs employing helical steam generator tubes are described in Thome et al., “Integral Helical-Coil Pressurized Water Nuclear Reactor”, U.S. Pub. No. 2010/0316181 A1 published Dec. 16, 2010 which is incorporated herein by reference in its entirety.
In some integral PWR designs, the steam generator outputs dry single-phase steam directly suitable to drive a turbine or other steam-driven machinery. Alternatively, if the steam generator outputs wet steam or a steam-water mix, then it can be dried in an external steam drum. See, e.g. Shulyak, “Westinghouse Small Modular Reactor Development Overview”, presented at the Interregional Workshop on Advanced Nuclear Reactor Technology for Near Term Deployment, International Atomic Energy Agency (IAEA), Vienna, Austria, Jul. 4-8, 2011.